CVE-2019-20432 in File System
Summary
by MITRE
In the Lustre file system before 2.12.3, the mdt module has an out-of-bounds access and panic due to the lack of validation for specific fields of packets sent by a client. mdt_file_secctx_unpack does not validate the value of name_size derived from req_capsule_get_size.
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Analysis
by VulDB Data Team • 01/27/2020
The Lustre file system represents a high-performance distributed storage solution widely deployed in enterprise environments and scientific computing clusters. This vulnerability affects versions prior to 2.12.3 and specifically targets the Metadata Target (MDT) module which serves as the core component responsible for managing file metadata and coordinating client requests. The flaw manifests as a critical out-of-bounds memory access condition that can lead to system panics and complete service disruption. The vulnerability stems from inadequate input validation within the mdt_file_secctx_unpack function, which processes security context information from client requests. When processing packets containing security attributes, the system fails to properly validate the name_size field obtained through req_capsule_get_size, creating an exploitable condition that allows malicious clients to trigger memory corruption.
The technical exploitation of this vulnerability occurs when a client sends specially crafted packets containing malformed security context data to the MDT module. The mdt_file_secctx_unpack function extracts the name_size value from the packet without proper bounds checking, allowing an attacker to specify an arbitrary size that exceeds the allocated buffer boundaries. This lack of validation creates a classic buffer overflow scenario where the system attempts to read or write memory beyond the intended allocated space. The vulnerability maps directly to CWE-129 Input Validation and CWE-787 Out-of-bounds Write, both of which are fundamental security weaknesses in software development practices. The absence of proper parameter validation in the MDT module represents a failure in defensive programming principles and input sanitization that should be implemented at every layer of the system architecture.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise the entire storage infrastructure. When triggered, the out-of-bounds access can cause the kernel to panic, resulting in complete system crashes that require manual intervention and system restarts. In large-scale deployments, this vulnerability could affect hundreds or thousands of nodes simultaneously, leading to cascading failures across the distributed storage cluster. The panic condition typically manifests as kernel oops messages and system reboot cycles, disrupting data access for all cluster users. Organizations relying on Lustre for critical workloads face significant business disruption risks, particularly in environments where continuous availability is essential for research, financial transactions, or industrial operations. The vulnerability also provides an entry point for more sophisticated attacks, as system crashes can be leveraged to gain additional system information or to establish persistent access through subsequent exploitation attempts.
Mitigation strategies for this vulnerability require immediate patch deployment to upgrade affected Lustre installations to version 2.12.3 or later, which includes proper validation of the name_size field. System administrators should implement network segmentation and access controls to limit client connectivity to MDT modules, reducing the attack surface available to potential attackers. Monitoring solutions should be deployed to detect anomalous packet patterns that might indicate exploitation attempts, particularly focusing on unusual name_size values in security context requests. The vulnerability also highlights the importance of implementing comprehensive input validation across all system components and demonstrates the necessity of regular security assessments for distributed storage systems. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious activity patterns consistent with this type of buffer overflow exploitation. Additionally, regular security training for system administrators and developers emphasizes the critical importance of input validation and defensive programming practices to prevent similar vulnerabilities from emerging in future code releases.